Chain shifting device for cycles



May 9, 1950 v. E. NEDHAM CHAIN SHIFTING DEVICE FCR CYCLES Filed oct'.11, 1948 nventor BMM Attorney! Patented May 9, 1950 CHAIN SHIFTINGDEVICE FOR CYCLES Victor Ernest Needham, Wilford, England, assignor toThe Birmingham Small'Arms Company Limited, Small Heath, England, aBritish Company Application October 11, 1948, Serial No. 53,950 In GreatBritain October 18, 1947 4 Claims. 1

This invention relates to chain shifting devices for cycles of the kindin which the chain is shifted or displaced from one to another ofsprocket wheels of different size mounted on the rear wheel hub of thecycle for the purpose of obtaining a variable gear, the mechanismusually being contrived as an attachment to the cycle and comprising ajockey sprocket and a chain tensioning sprocket carried by a pivotedarm, the device being -operable by means of a cable or Bowden wiretransmission mechanism.

In chain shifting devices of the aforesaid kind it has been proposed tomount the jockey sprocket and pivoted tensioning arm on a horizontaltube secured to a bracket which is attached to the cycle frame, the saidtube containing a coil spring one end of which is anchored to the tubewhile the other end exerts a lateral thrust against the jockey sprocket.Thus the tube, the spring and the jockey sprocket together form thechain shifting device, lateral movement to the jockey sprocket and thechain tensioning sprocket being in one direction imparted by the springand in the opposite direction by a flexible transmission cable, but insuch chain shifting structure the tube has to be relatively long toaccommodate the spring and provide for the necessary lateral movement ofthe jockey sprocket, so that outward protrusion of the tube renders itliable to damage.

According to this invention the aforesaid objection is overcome byslidably mounting a jockey sprocket or pulley on a rod or tube whichconstitutes a combined tension arm pivotally attached to and dependingfrom the cycle frame, said rod or tube being bent to form a portionextending in a direction normal to the remainder thereof and for adistance sucient only to provide for the necessary axial movement of thejockey sprocket or pulley, a coiled compression spring associated withthe rod or tube for imparting in one direction axial movement to thejockey sprocket or pulley, and means for imparting movement thereto inan opposite direction through the medium of a flexible transmissioncable.

In the accompanying sheet of explanatory drawings:

Figure 1 is a side elevation of a chain shifting device constructed inaccordance with the features of this invention;

Figure 2 is an end elevation of Figure 1;

Figure 3 is a sectional end elevation of the clevice on an enlargedscale;

Figure 4 is a fragmentary plan View of the slotted end of the gear tube,and

Figure 5 is a sectional View of the tension spring carrier and gear tubeadjusting clip.

According to one convenient mode of carrying the invention into effectas shown in the drawings, a bracket or supporting member I for the chainshifting device is attached to the rear fork end 3 of the cycle frame bymeans of a slotted portion engaging with the spindle 5 of the Wheel huband a xing screw 1. A tube 9 is attached to the bracket I by means of anadjusting clip II which constitutes part of a tension spring carrier, ashereafter described. A short portion of the tube 9 is bent in adirection normal to the length of the tube, and has slidably mountedthereon a jockey sprocket or carrier pulley I3, said pulley beingsupported by bearing cones I5 and IT mounted on a carrier bush I9, whichalso supports two plates 2I constituting a combined guide for ellectinglateral displacement of the cycle chain from one wheel sprocket toanother.

The aforesaid portion of the tube 9 has formed therein two diametricallyopposed slots 23, as seen in Figures 3 and 4, adapted to receive a pinor peg 25, the ends of which are anchored in slots formed in the carrierbush I9. To the peg 25 is secured through a ferrule one end of the innerWire 21 of a flexible transmission cable, the outer sheath 29 of thecable being retained by an adjuster 3l adapted to be screwed into theend of the tube 9 remote from the slots 23. Within the tube 9 isdisposed a coiled compression spring 33 which surrounds the inner wire21, one end of the spring abutting against the peg 25 While the otherend abuts against the cable adjuster 3|.

As previously stated the tube 9 is attached to the bracket I by means ofan adjusting clip II which constitutes part of a tensioning springcarrier. Viewed from the end this clip is substantially of U-shape, theclosed end encircling the tube 9 and being xed thereto by welding orother suitable means, while the two limbs each have a co-axial holeformed therein by which the clip is freely mounted on a sleeve 35.Through a hole in the bracket I is inserted the threaded stem part of acarrier pin 31 over which is passed the sleeve 35, said sleeve beingclamped between the face of the bracket I and a nut 39. The head of thepin 31 is enlarged to form a shoulder abutting against the rear face ofthe bracket I, and on said head of the pin is mounted the coils of atensioning spring 4I, one end of which is anchored in a slot formed inthe head of the pin 31 while the other end of the spring is shaped tocontact with the tube 9. In operation the tube 9 swings about the pivotconnection between the 3 limbs of the bracket Il and the sleeve 35 intaking up slack when the chain is being transierred by the pulley i3from one wheel sprocket to another of different size, the chain tensionbeing maintained by the spring 4 l.

As shown in Figure 3, the chain shifting device is in the extremeoutward position (i. e. in an axial direction away from the hub) inwhich the high gear is engaged with the chain on the smallest hubsprocket. In this position the inner wire 21 has been fully retracted bythe gear actuating lever (not shown) and the spring 33 is compressed.When the normal or low gear is selected, the chain is transferred,during travel, to a sprocket of larger size by axial movement of theshifting device imparted by the spring 33, which effectively transfersthe chain when such is being lifted on to a sprocket of larger size.

By arranging the chain shifting device on a length of cylindrical tubinghaving a portion thereof extending axially of the wheel sprockets for aminimum distance required to permit the necessary movement beingimparted to the jockey sprocket or pulley, outward protrusion of thedevice and consequently the possibility of damage is substantiallyreduced.

It will be appreciated that the coiled compression spring 33 may bedisposed externally of the chain shifting and tensioning arm, in whichcase the ends of the spring could be arranged to contact respectivelywith the carrier bush I9 and a suitable abutment in the form of a collarsecured to the arm and located between thebush i9 and the point ofcontact with the arm of the spring 4l.

Having thus described my invention, what l claim as new and desire tosecure by Letters Pattent is:

1. A combined chain shifting and tensioning device for cycles,comprising a rigid arm having means for pivotally attaching it to acycle frame to depend therefrom, said arm having a short portionintegral therewith and extending in a direction normal to the remainderthereof, a jockey wheel mounted on said short portion of the arm forrotation and axial movement thereon, a coil spring extendinglongitudinally of the arm concentrically to its longitudinal axis andacting on the jockey wheel to impart axial movement thereto in onedirection, means including a ilexible transmission cable extendinglongitudinally of said arm concentrically to its longitudinal axis andconnected to the jockey wheel for imparting axial movement thereto inthe opposite direction, and means acting on the arm to swing the jockeywheel in chain-tensioning direction.

2. A combined chain shifting and tensioning device for cycles,comprising a rigid tube having means for pivotally attaching it to acycle frame to depend therefrom, said tube having a short 4 portionintegral therewith and extending in a direction normal to the remainderthereof, a jockey wheel mounted on the short portion of the tube forrotation and axial movement thereon, a coil spring extendinglongitudinally of the tube concentrically to its axis and acting on thejockey wheel to impart axial movement thereto in one direction, meansincluding a exible transmission cable extending axially within the tubefor imparting axial movement to the jockey wheel in the oppositedirection, and means acting on the tube to swing it and the jockey wheelin chaintensioning direction.

3. A combined chain shifting and tensioning device as dened in claim 2,wherein said coil spring is a compression spring and is enclosed by andextends axially within said tube.

4. A combined chain shifting and tensioning device for cycles,comprising a rigid arm having a short integral portion dependingtherefrom and extending in a direction normal to the remainder thereof,a jockeyy wheel mounted on said short depending portion of the arm forrotation and axial movement thereon, and means for pivotally attachingsaid arm to a cycle frame for chaintensioning movement of the jockeywheel comprising a bracket having means for securing it to a cycle frameand having an aperture therein, a carrier pin extending through saidaperture in the bracket and having a head abutting against one side ofthe bracket and a threaded part at the other side of the bracket, asleeve surrounding the threaded part of said pin, a clip fixed to saidarm and mounted on the sleeve to rotate freely thereon, a tension springsupported by said pin, the latter having a slot in its head foranchoring one end of the spring, the other end of the spring engagingsaid arm and acting thereon to swing the arm in chain-tensioningdirection, and a nut on the threaded part of said pin and engaging thesleeve for securing the pin and sleeve against the respective sides ofthe bracket and thereby prevent rotation of the pin and sleeverelatively to the cycle frame.

VICTOR ERNEST NEEDHAM.

REFERENCES CITED The following references are or record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,010,248 Winkler r Aug. 6, 19352,187,368 Todrys Jan. 16, 1940 2,428,166 Letourneur Sept. 30, 1947FOREIGN PATENTS Number Country Date 444,999 Great Britain Apr. 1, 1936

